I. Field of the Invention
The invention relates to a seal with a dynamic brush to provide a seal between a rotor and a stator.
Seals with brushes of this type are used in the main to produce a seal between a compartment containing air and a compartment containing a mixture of air and oil or a seal between two compartments containing air in high and low pressure compressors and in high and low pressure turbines.
More precisely, the invention relates to a seal with brush consisting of non-metallic textile insulators, capable of providing a seal for an air gap between a rotor and a stator incorporating a container for the textile insulators fixed on to the rotor or the stator, the textile insulators being subjected, on one side, to an upstream pressure and on another side to a downstream pressure, the upstream pressure being greater than the downstream pressure.
II. Description of Related Art
The seals currently used in these applications are seals of the labyrinth type which incorporate annular teeth called tongues. When inserted in a ring, in softer material called abradable, these tongues produce a plurality of cross-section restrictions generating a loss of charge and thus a reduction of output. With such a seal, permeability in air is high and accordingly the turbomachine consumes oil, which leads to costs and is also toxic for the environment.
We are also familiar (EP 1 517 006) with a seal with a brush which provides sealing of the cavity for sampling air at the cabin. This cavity is delineated first by an external shell of the compressor and an annular structure connected to the shell and second by the external housing of the diffuser grid, an abutment connected to the external housing and an external shell of the motor housing. The seal incorporates textile insulators which extend radially towards the outside and which are supported on the inner surface of a cylindrical seal forming an integral part of the annular structure and surrounding the seal with a brush. However, a seal of this type produces a static seal in which there are no problems with wear.
We are also familiar (U.S. Pat. No. 5,400,586) with a seal with a self-adjusting brush for a gas turbine combustion chamber. The gas turbine incorporates a combustion chamber incorporating at its output end a transition part spaced from a first stage pipe. A seal with a brush provides a seal between the transition part and the first stage pipe. The seal incorporates a sealing shell supported either by the transition part or by the first stage pipe. A gasket incorporates textile insulators which come into contact with the sealing shell to make the space included between the transition part and the first stage pipe leakproof. A seal of this type also produces a static seal and there are no problems with wear.
We are again familiar with seals with a metallic brush which have been used with turbomachine applications since the fifties. The most important point to note about this technology is the need to butt the hairs against a barrier resistant to pressure (the rear ring). The consequence is a stiffening of the brushes proportional to the applied pressure, which can cause accelerated wear of the brushes if the gap ceases to exist under these conditions. The least contact with the rotor leads to rapid wear of the seal and deterioration of the sealing properties.